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Microsoft Teams not capturing traffic


My system info:
Ubuntu 20.04 OS running in VMWare.

Fiddler everywhere will not capture Microsoft Teams live traffic. I see under the header for the .saz file under transport that the Connection is closed.  I have installed the fiddler root cert on the system successfully and successfully imported the root cert in Firefox. At first Teams would not even connect on local app download when FE was capturing live traffic, but I finally got Teams to connect when I added https//teams.microsoft.com URL to the Connection tab under the bypass URLs when running fiddler.

Need help getting FE to capture live traffic. I have attached the .saz file which captured traffic when Teams was running.

The password for the .SAZ file is: 1234


(44.7 KB)

Just to add I have included the following configuration:



Hello Jaime,

The issue appears because MS Teams is not working well alongside OS system proxies (and all proxies - see this statement from Microsoft). That said, in your particular case, Fiddler Everywhere installs and trusts the root certificate in the OS folder that most applications are using, but as you might guess, this is not the place where MS Teams is looking for the CAs. MS Teams is using Electron CA management, so the folder where the MITM trust certificate should be installed is in ~/.pki/nssdb

You should move the certificate to that folder and use the certutil to install and trust it. 

If you don't have certutil, install it by using the following command:

sudo apt install libnss3-tools

Then use the following command to install and trust the certificate. The below command assumes that you already have the root certifiacte installed at  /usr/share/ca-certificates/extra but if that is not the case, then do it (so that you could capture traffic from other applications and not only from MSTeams).

certutil -A -n "ROOT-CA" -t "TCu,Cu,Tu" -i /usr/share/ca-certificates/extra/FiddlerRootCertificate.crt -d sql:/home/${USER}/.pki/nssdb

Finally, restart Fiddler Everywhere, and you should be able to see traffic captured from MSTeams.

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